System of control for single-phase alternating-current motors



R. E. HEELMUND. SYSTEM OF CONTROL FOR SINGLE PHASE ALTERNATING CURRENTMOTORS. APPLICATION FILED JUN-E15, 1917- 1,339,928, 1 Patented May11,1920.

4 SHEETS-SHEET 1- WITNESSES: INVENTOR R. E. HELLMUND. SYSTEM OF CONTROLFOR SINGLE PHASE ALTERNATINGCURRENT MOTORS. APPLICATION FILED JUNE I5,1917.

1,339,928. Patented May 11, 1920,

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. BY I ATI'ORNEY R. E. HELLMUND.

SYSTEM OF CONTROL FOR SINGLE PHASE ALTE RNATING CURRENT MOTORS,APPLICATION FILED JUNE 15, 1917.

1,339,928. Patented May 11,1920.

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INVENTOR ATTORNEY R. E. HELLMUND.

SYSTEM OF CONTROL FOR SINGLE PHASE ALTERNATING CURRENT MOTORS.APPLICATION FILED JUNE 15, 1917.

1,339,923 Patented May 11, 1920.

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ATTORNEY UNITED STATES PATENT OFFICE.

BUDOLF E. I-IELLMUND, OF SWISS'VALE, PENNSYLVANIA.

SYSTEM OF CONTROL FOR SINGLE-PHASE ALTERNATING-GURRENT MOTORS.

To all whom it may concern:

Be it known that I, RUDoLr ,E. IIELL- MUND, a subject of the Emperor ofGermany, anda resident of Swissvalve, in the county of Allegheny andState of Pennsylvania, have invented a new and useful improvement inSystems of Control for Single-Phase Alternating-Current Motors, of whichthe following is a specification, this application being a continuationin part of application Serial No. 33,481, filed June 11, 1915.

My invention relates to systems of control for alternating-currentmotors of the doubly-fed compensated commutator type, and it has for itsobject to provide a system of the character described containing two ormore motors wherein relatively few control switches are employed,relatively few terminal leads are necessary, and wherein the controlswitches shall. operate solely in circuits carrying only a portion ofthe fullload armature current of one of the motors.

111 the accompanying drawing, Figures 1, 3, 10, 12 and 14- arediagrammatic views of compensated commutator motors, together with theirattendant supply and control circuits, constructed in accordance withdifferent embodiments of my invention; Figs. 2, 4, ll, 13 and 15 aresequence charts illustrating the mode of switch operation in theaccompanying circuits; and Figs. 5 to 9, inclusive, are simplifieddiagrammatic views of the motor and system shown in Fig. 1, illustratingin greater detail the method of acceleration employed therein.

In the development of the alternatingcurrent commutator motor,especially for traction purposes, it has been found neces sary,especially where resistance leads are dispensed with, to providecompensating windings for controlling the commutation. Many advantagespertain to what is known as the doubly-fed motor, wherein either aninterpole or a compensating winding is connected in, series with themain field and or mature windings and a tap is provided from a pointintermediate the compensating field winding and the remainder of themotor to the source, so that the voltage impressed upon the compensatingfield winding shall have a value complementary to that of the voltageimpressed upon the remainder of the motor windings. It has been founddesirable to provide the compensating or crossfi ld Winding ith m re tuns than the a Specification of Letters Patent.

Patented May 11, 1920.

Application filed June 15. 1917. Serial No. 174,885.

mature winding so that, as a result of the transformer actiontherebetween the crossfield winding shall carry smaller. currents thanthe armature winding, the differential current reaching the source viathe intermediate or tap connection. With a motor of the characterdescribed, when it is desired to entirely disconnect from the sourcerelatively small. switches may be employed in the connections betweenthe terminals of the cross-field winding and the source because each ofthese connections carries only a portion of the load current, butrelatively large switches are required in the connection from the otherterminal of the motor to the source because full-load armature currentis here encountered.

By my invention I employ two or more motors or the characters indicated,ureterably of similar size and operating characteristics, connectingboth terminals of both cross-field windings to the current sourcethrough suitable control means and connecting the remaining motorterminals directly together. By this connection, assuming instantaneousvalues, a portion of the load current flows into the outer terminal ofthe cross-field winding of one motor and the remainder of the loadcurrent flows into said motor via its intermediate connection. Afterpassing through said motor, the entire load current flows through thearmature and main field winding of the other motor and then divides, aportion passing back to the source via the intermediate connection andthe remainder via the cross-field win-ding of the last motor. By placingall of the control switches in the connections to the source, I amenabled to dispense entirely with control switches which carry full-loadarmature current and, at the same time, I obtain an exceedingly simpleand flexible system of voltage control for the motors. An intermediateor neutral connection is preferably provided from a point intermediatethe two motors to a point of corresponding potential in the source, saidneutral connection normally being disconnected or carrying onlyunbalanced currents but pro viding means whereby, in case of emergency,either motor may be entirely disconnected and the railway vehicleoperated solely by the remaining motor.

By my invention, the voltages impressed upon the cross-field windings ofthe two motors may be somewhat difi'erent for cerany practicalimportance.

tain accelerating notches, but nevertheless, the motors will exert-thesame torque because the armatures are connected in series and aretherefore supplied with the same current and, further, because of thetransformer effect between each armature and its associated crossfieldwinding, whereby each of the latter will also have practicallv the samecurrent as the other. The different voltages impressed upon thecross-field windings will slightly alter the compensating effect and thecommutating conditions in the two motors but not sufficiently to have Myinvention comprises further details and modifications alon theabove-mentioned lines, as will hereinafter more fully appear.

Referring to Fig. 1 for a more detailed understanding of my invention, Ihave shown two motors of the compensated commutator type at 14 and 15.The motor 14 is provided with an armature 16, a mainfield winding 17 anda cross-field winding 18 and, in like manner, the motor 15 is providedwith an armature 19, a main-field winding 20 and a cross-field winding21. Current for the motors 14 and 15 is derived from any suitablesource, such, for example, as the secondary winding 22 of a transformer23. Energy is supplied to the outer terminal of the cross-field winding18 through a control switch 1. The voltage of the other terminal of thecross-field winding 18 may be adjusted by suitable control switches 2, 3and 4 and a preventive device 24 of the usual form. The outer terminalof the cross-field winding.21 is connected to the transformer winding22, not onl through a control switch 9 but also throug a resistancemember 25 which may be short circuited by a switch 10. The voltagesimpressed upon the inner terminal of the crossfield winding 21 may beadjusted by suitable control switches 6, 7 and 8 and a preventive device26. The armature windings 16 and 19 and the main field windings 17 and20 are all connected in series relation between the inner terminalsofthe cross-field windings 18 and 21. The direction of current flowthrough the main field windings, with respect to the armature windings,may be reversed by a suitable switch 27 when desired. For repulsionoperation, the armature windings 16 and 19 may be short circuitedthrough a resistance member 28 and a switch 5.

Having thus described the arrangement of the circuit shown in Fig. 1,the operation is as follows, referring to the sequence chart of Fig. 2and Figs. 5 to 9, inclusive. At the outset, switches 1, 5 and 9 areclosed, (Fig. 5) whereupon the motors 14 and 15 are connected forrepulsion operation with a mini munrimpressed voltage, and theresistance member 25 is included in circuit. The resistance member 25 isthen eliminated by closing the switch 10, thus providing the firstrunning position (Fig. 6). The voltage applied to the cross-fieldwindings Band 21 is then raised by a suitable manipulation of theswitches 2, 3, 4, 6, 7 and 8, and the repulsion connection through theswitch 5 is opened, whereupon the motors are connected for the secondrunning position for doublyfed operation (Fig. 7). The voltage impressedupon the cross-field windings 18 and 21 is then reduced by even steps,the voltage on the armatures 16 and 19 and the main field windings 17and 20 being raised accordingly. (Figs. 8 and 9.)

As ordinarily designed, the cross-field windings 18 and 21 would containsubstantially twice the number of turns included in the armaturewindings 16 and 19. Accordingly, substantially one-half the workingcurrent would flow through the switches 1 and 9 and the other half wouldflow throu h the switch 2 or the switch 4 and through t e switch 6 orthe switch 8. None of the control switches therefore are ever calledupon to open circuits carrying full-load current.

Referring to the form of my invention shown in Fig. 3, two motors 14 and15 are provided and are connected, in a general manner, similar to thatshown in Fig. 1, with the exception that the main field windings 17 and20 are normally connected directly between the armatures 16 and 19through individual reversing switches 27 and 28, disconnecting switches29 and 30 and the actuating windings of a limit switch 40 connected tooperate the control switches of the associated motors in accordance withany of the known systems of automatic limit-switch control.

Each of the switches 29 and 30 is provided with an emergency contactmember 42. The emergency contact member of the switch 29 is connected,through the actuating winding of a limit switch 44 to the tap 6 and, inlike manner, the emergency contact member of the switch 30 is connected,through the actuating winding of a limit switch 43, to the tap 4. Thecontact members of the limit switch 44 are connected in series with onepair of those of the limit switch 40, and those of the limit switch 43in series with the other pair of those of the limit switch 41. Theswitches 43 and 44 are preferably given higher settings than the switch40.

Under normal conditions, the potentials and currents in the system willbe in a state of equilibrium, and current will flow across directl fromthe switch 29 to the switch 80. I a motor, such, for example, as 14, isdisabled, the switch 30 is thrown to the emergency position, whereuponthe motor 15 is connected for doubly-fed operation between the taps 4and 9. The motor 15 there fore receives a greater impressed voltage thanthat encountered in normal operation,

the latter voltage being substantially half ofthat between the taps 1and 9. During normal operation, the actuating winding of the limitswitch 43 was unenergized, so that said switch remained in the closedposition comes into operation and, with its higher setting and seriesconnection with the contacts of the switch 40, supersedes the'latter infunction and assumes control of the switches 5, 6, 7 8 and 9. It willthus be seen that, when operating on one motor, a greater voltage and agreater current are impressed thereupon than in normal operation,resulting in the development of the necessary torque.

It will be observed that, because of the desired segregation between thetwo motors, it is impossible to provide a common repulsion connectionfor'the two armatures and I therefore provide the respective armaturewindings with short-circuiting resistance members 28 and 28 that arecontrolled, re-

spectively, by suitable switches 5 and 5.

It will be further noted that, with the circuit shown in Fig. 3, it isnecessary to provide each motor with but five leads, as compared withthe six leads commonly employed hitherto in like relations.

The present disclosure diifers from that set forth in theabove-identified application, of which this is a continuation in part,in the arrangement and connections of the current relays 40, 43 and 44.

The system shown in Fig. 10 is, in many respects, the same as that shownin Fig. 1 but an additional accelerating step and lowspeed runningposition is obtained by first passing current through the armaturewindings 16 and 19 in the reverse direction from that employed in normaloperation, thus obtaining what may be termed a sub-repulsion or reversedoubly-fed connection. The motors are subsequently accelerated in themanner indicated in Fig. 1.

Referrin to the form of my invention shown in ig. 12, the connectionsare the same as shown in Fig. 1 with the exception that the voltagesupplied by the outer tap 32 may be adjusted by suitable switches 9, 53and 54 and a preventive device As pointed out in the preliminaryexplanation, the effect of the unbalancing thus produced in the systemis largely eliminated by reason of the fact that the armature windings16 and 19 are connected in series with each other and therefore carrythe same current, and each of them is inductively related to itsassociated cross-field winding.

Under certain conditions, I find it highly desirable to maintain an evenvoltage balance in the system at all times and to effect a portion ofthe voltage control, under normal operation, by manipulating transformerturns in the central portion of the secondary winding. If then, for anyreason, it becomes necessary to disconnect one of the motors, the abovementioned central group of control switches is available for the speedcontrol of the remaining motor, )roviding additional steps and renderingpossible the application of a voltage higher than normal thereto inaccordance with the principles pointed out in connection with Fi 3.therefore connect as shown in 14, wherein the two motors 14 and 15 arear ranged to derive energy from a secondary winding 22 split into halves22 and 22. The motors 14 and 15 are normally connected in seriesrelation through disconnecting switches 29 and 30, and a neutral wire 31is rendered inoperative because of the open position of suitableemergency con trol switches 36 to 41, inclusive. The adjacent terminalsof the windings 22 and 22" may be directly connected through a switch 55or indirectly connected through a switch 56 and resistance members 42and 43. The taps 44 and 45, symmetrically located in the windings 22 and22 may be directly connected through a switch 57.

As shown in the sequence chart of Fig. 15, the switch 57 is closed atthe outset, thus eliminating the winding portions 34 and 35 and reducingthe voltage supplied to the switches 4 and 6 to a minimum value. At thefourth accelerating position, the switch 56 is closed, whereupon alarger number of turns is included between the switches 4 and 6 but thecurrent is reduced in value by the resistance members 42 and 43. At thesixth accelerating position, the resistance members 42 and 43 areeliminated by closing the switch 55, whereupon the maximum voltage isobtained between the switches 4 and 6. The voltage supplied to theintermediate taps and outer terminals of the doubly-fed motors 14 and 15is adjusted in the usual manner by the manipulation of the switches 1 to4, inclusive, 6, 7, 8 and 9.

If now, for example, the motor 15 is dis abled, the correspondingdisconnecting switch 30 is opened, and the vehicle is operated by themotor 14 through the neutral wire 31 and the emergency switches 36 to41, inclusive. lVhen low operating voltage is required, the switch 38 isclosed, and only the voltage between the taps 1 and 44 is employed.lVhen a greater voltage is desired, the closing of the switch 36 causesthe entire winding 22 to be active, but its effective voltage is cutdown by the member 42. Further voltage increase is next obtained byclosing the switch 37, connecting the winding 22 directly in circuit. Inthe final operating condition, to obtain abnormal voltage on the motor14, the switch 41 or the switches 38 and 57 are closed, thus adding thevoltage of the winding 35 to that of the half secondary member 22. Theswitches 1, 2, 3 and 4 are also employed, in the usual manner, duringemergency operation of the motor 1 1-.

While I have shown my invention in a variety of modifications, it willbe apparent to those skilled in the art that it is susceptible ofvarious minor changes and modifications without departing from thespirit thereof, and I desire, therefore, that only such restrictionsshall be placed thereupon as are imposed by the prior art or arespecifically set forth in the appended claims.

I claim as my invention: 7

'1. In a system of control, the combination with a supply-transformerwinding and a plurality of alternating-current motors of the commutatortype severally having armatures, exriting and inducing field windings,of means for connecting the armatures and exciting field windings of allmotors in series relation across a middle section of the transformerwinding, and means for connecting each of said inducing field windingsacross an adjusting outer transformer section contiguous to said middlesection, whereby the voltage of all motors may be changed bysuccessively and independently varying the voltage of said inducingfield windings.

2. In a system of control, the combination with a supply-transformerwinding and a plurality of alternatingcurrent motors of the commutatortype severally having armatures, exciting and inducing field windings,of means for connecting certain of the windings of all motors in seriesrelation across a middle section of the transformer winding, means forconnecting the remaining windings across outer transformersections'contiguous to said middle section, a limit switch normallyconnected in the series circuit, a plurality of normally disconnectedlimit switches, and cut-out means for simultanetures, exciting andinducing field windings, r

of means for connecting the armatures and exciting field windings of allmotors in series relation across a middle section of the transformerwinding, and means for connecting the inducing field windings acrossouter transformer sections contiguous to said middle section, a limitswitch normally connected in the series circuit, a plurality of normallyinoperative limit switches of higher setting than said normallyconnected limit switch and each having one terminal connected to one oftwo points located redetermined distances on the respective sides of thetransformer electrical mid-point, and a plurality of cut-out switchesfor simultaneously cutting-out the respective motors, together with saidnormally connected limit switch, and cutting-in one of said normallydisconnected limit switches to thus permit complete operation of anothermotor from more than half of the transformer Winding.

In testimony whereof I have hereunto subszcribed my name this 26th dayof May, 191

RUDOLF E. HELLMU ND.

